A total of 93 extant and five extinct subpopulations were identified across the natural range of O. nerka. The assessors used a combination of ecoregional information (i.e., based on differences in marine and freshwater habitat) and the degree of genetic divergence between known spawning locations, using an Fst value of 0.04, representing a threshold level of gene flow between putative subpopulations of less than or equal to one effective migrant per year. The five extinct subpopulations were based on Gustafson et al. 2007. While the assessors acknowledge that it is not straightforward to ascribe demographic or geographic distinctness to a subpopulation based on observed genetic distances, they feel it is the most appropriate methodology given the scale of the assessment and the paucity of observations of stray rates among the spawning locations considered in this assessment. For the amendment completed in 2011, we split a number of British Columbia subpopulations described in the original 2008 assessment based on additional input from experts. In the 2008 assessment, this subpopulation was named "FRASER RIVER, BOWRON," and only a name change recognizing the run timing has occurred. For a complete description of the approach and methods used for identifying units and the underlying assumptions, please refer to the supporting documentation.Follow the link below for a PDF of the supporting documentation.

Subpopulation naming convention: Subpopulation names consist of an ecoregion name in upper case with any subdivision of the ecoregion by other criteria (e.g. genetic divergence) indicated in proper case after a colon.

Justification:
This subpopulation was evaluated against relevant A, B and D criteria. Recent escapement trends at individual monitoring sites were analyzed and results were scaled upwards to characterize the Red List status of the subpopulation against A2 criterion (i.e., based on the rate of change in adult abundance over three generations, or 12 years for this species). The rate of change applied to this subpopulation, assessed over 1 site(s), was -69%. It therefore qualifies as Endangered against criterion A2. For evaluation against B2 criterion, we estimated the area of occupancy and the number of extant locations for the subpopulation. Area of occupancy was estimated on a one kilometer square grid overlaid on the nursery lake(s) and freshwater river habitat. This surface area estimate is meant to capture habitat occupied for spawning and rearing by both lake- and river-type life histories. The number of extant locations was the sum of the total number of known nursery lakes and distinct spawning regions supporting the subpopulation. The surface area of freshwater habitat supporting this subpopulation (33 km2), the number of extant locations (2 lakes and/or distinct spawning areas), and its observed rate of change in adult abundance described above qualifies this subpopulation as Endangered against the B2ab(v) criteria. The current abundance of mature adults in the subpopulation qualifies it as Least Concern against the D1 criterion. See additional supporting document for data sources, trend model parameters, complete description of methods and assumptions, key threats specific to each threatened and near threatened subpopulation and general conservation measures.Follow the link below for a PDF of the additional supporting documentation.

The current distribution of Oncorhynchus nerka extends from approximately 45-70°N to 140°E-125°W longitude. The species has been recorded from Russia, United States, Canada, and Japan, although the Japanese populations are likely to have resulted from introductions; Japan is therefore not considered to be part of this species' natural range.

See the additional supporting documentation (particularly Figures 1 & 2, and Appendices 1 & 2) for details on the range of this species and of each of the 98 subpopulations identified. Follow the link below for a PDF of the additional supporting documentation.

At the species level, the population is believed to be stable; however, some subpopulations are declining. For more details on subpopulation size estimates and trends, see the additional supporting documentation (particularly Appendix 2). Follow the link below for a PDF of the additional supporting documentation.

The species exhibits a great variety of life history patterns. It has a genetically diverged life history form called “kokanee” that lives its entire life within freshwater, but this assessment includes only anadromous populations commonly referred to as “sockeye” or “red salmon”. Sockeye are born in gravel nests in rivers or lakes and the majority of life history forms rear as juveniles for one to three years in freshwater before migrating to the ocean. Some sockeye assume a river-type life history and rear in a river channel, while others are lake-type and rear in a lake environment. Primary prey during this life history stage include zooplankton and stream invertebrates. Some sea-type populations migrate within one to three months following emergence, and these make extensive use of estuaries. Most populations spend one to three years in offshore feeding areas where they grow to maturity (ca. 50-60 cm total length, 2.5-3.0 kg weight). Diet in the ocean consists primarily of zooplankton (copepods and euphausiids), but their diet also includes squids and fishes. Natural predators during this period in their life history include salmon sharks (Lamna ditropis) and Daggertooth (Anotopterus nikparini). Foraging individuals mix among populations both within and between Asia and North America, but at maturity they all migrate back toward their natal freshwater habitat where they spawn and die. The return to natal habitat and the isolation of spawning populations results in considerable genetic differentiation and adaptation to local conditions. Many fish are intercepted by fishers during the homeward, spawning migration, and natural predators include seals, sea lions and bears. Spawning occurs in late summer and autumn, in lake outlet or lake tributary streams or along lake beaches in finer sediments where subterranean upwelling occurs or among boulders on wave-aerated shores. River-type sockeye spawn in river channels not associated with lakes. Adults display bright red bodies and green heads. Males compete with each other for access to females. Females compete with each other for gravel sites where they build nests, deposit eggs (fecundity typically ranges from 2,000-5,000 eggs), and briefly guard the redd. Median population size for the species is ca. 6,000 individuals. Reviews of life history and ecology of the species appear in Smith et al. (1987), Burgner (1991), Wood (1995) and Quinn (2005).

A certain percentage of sockeye are captured and killed exclusively for their roe (eggs, caviar). This occurs primarily in the Russian portion of their natural range, and the fishery is illegal and the take is unreported.

1.
Many subpopulations of sockeye in British
Columbia were found to be threatened based on this
assessment. Fisheries and Oceans Canada (DFO) is responsible for salmon
management and is currently formulating conservation units (Holtby and Ciruna,
unpublished manuscript) and initiating new policy (e.g,. Wild Salmon Policy)
and procedures to stem the loss in diversity (DFO 2005, Irvine and Fraser 2008). Two locations of
sockeye salmon, SakinawLake and CultusLake, have been assessed and listed as
Endangered by the Committee on the Status of Endangered Wildlife in Canada
(COSEWIC). However, the federal government has
declined protection under the Species at Risk Act (SARA) due to the social and
economic costs of closures to the fishery (Irvine et al. 2005). We encourage
COSEWIC and DFO to focus attention on those subpopulations that we identified
as threatened in this IUCN assessment.

2.
We considered OzetteLake, LakePleasant and QuinaultLake
sockeye salmon as individual spawning sites in a larger subpopulation
(SEASONAL UPWELLING). These lake systems are recognized individually as
Evolutionarily Significant Units (ESUs) by National Oceanic and Atmospheric
Administration (NOAA). The latter two sites were not included in the
genetic baseline applied in this assessment, thus we assumed all sites are
members of a larger, parent subpopulation. Further, we did not include OzetteLake
in our assessment given the recent escapement data available for the native
beach-spawning population at that location is obscured by repeated attempts at
establishing a tributary spawning population originating from broodstock taken
from outside the basin. We encourage efforts at expanding the range-wide
microsatellite-DNA baseline to include LakePleasant and QuinaultLake, and to investigate the status of
the native beach-spawning sockeye in OzetteLake.

3.
Most of the data used in our assessment, particularly in Alaska, were from large aggregate stocks
that may contain many (sometimes 100s) of individual spawning sites, and
hence may mask important dynamics occurring at small scales. While a number of
recent studies have shown that there is a significant degree of coherence among
populations within a given region, it is important to acknowledge that a
majority of the variability in vital rates are not explained by regional,
environmental drivers, and may result from localized threats, for example road
or other infrastructural development, or by different life history
characteristics which affect productivity. Where possible and feasible, we
recommend a more comprehensive monitoring approach that addresses dynamics at
the scale of individual spawning sites. An excellent example of this
approach is the Wood River system in Alaska’s Bristol Bay region, where a
combination of sampling approaches provides a more integrated monitoring system
that translates into a robust assessment of the status of the species in that
basin.

4.
Mixed-stock fishing is likely to be a key factor in the decline observed at
many sites and subpopulations in our assessment. We feel a key
priority is filling a gap in knowledge about composition of mixed-stock harvest
in coastal sockeye salmon fisheries. While a great deal of resources has been
invested in developing weak-stock management for Fraser River sockeye salmon
through the Pacific Salmon Commission and DFO, there has been much less
attention placed in other regions along the west coast of North America,
particularly in the regions where we found the greatest diversity of subpopulations.
We encourage continued investment in developing methods and protocols to
account for subpopulation composition of coastal fisheries targeting
sockeye salmon to help track harvest pressure at a biologically and
ecologically meaningful scale. Further, we encourage fisheries management
agencies to explore restructuring fisheries in a way that would result in
shifting fishing pressure from coastal regions to more terminal locations, thus
providing a more effective means of controlling fishing pressure at the scale
of individual subpopulations.

5.
Another leading factor threatening sockeye salmon are poor marine survival
rates. This has been documented in cases where smolt-to-adult survival rates
are estimated through intensive monitoring programs. This appears to be a
significant factor explaining declines in adult abundance across many locations
in the southern range of the species in North America.
While marine conditions have been shown to cycle based on climate forcing and
may, in fact, improve in future years, we feel it is important for those
managing salmon in this region to acknowledge that poor marine survival may
persist, particularly given projections based on global climate change.
Reversing declining trends in those subpopulations affected may require
increased attention to agents of mortality that are occurring at other life
history stages over which we have more local control.

6.
Many previous attempts at re-introductions of sockeye salmon have been
unsuccessful, and we feel any effort at captive breeding or inter-basin
transfers for re-introduction purposes should proceed with great caution. These
efforts, to the extent that they exist, are at best stop-gap measures and are
in no way a substitute for conserving the species in the wild. The lack of
success from the captive breeding of endangered Sakinaw sockeye salmon by DFO,
and endangered RedfishLake sockeye by NMFS, are
examples of the limitations to these expensive measures. Recent evidence of
re-establishment of anadromous runs of sockeye from remnant, isolated kokanee
populations following dam removal or modification (e.g., AllouetteLake in British Columbia) may offer hope in
re-establishing anadromous life histories in cases where dams have prevented
passage.

7.
Enhancement activities (particularly hatchery releases and spawning channel
construction) is likely to be a key factor in reducing abundance in
neighboring, small wild populations. In our assessment, we were unable to
functionally track both wild and enhanced sockeye salmon where they
intermingle. We strongly recommend adoption of integrated monitoring programs
that includes a robust marking program and monitoring efforts targeted toward
wild sockeye salmon populations that would provide the data necessary to
address the degree to which enhancement practices threaten wild sockeye salmon.
It is important to note that two large basins in our assessment (Fraser and Skeena) are all strongly. influenced by enhancement
activities, and these activities likely represent a key factor threatening many
neighboring subpopulations.

8.
While not addressed in the present assessment due to lack of data, we feel
there should be more focused research attention on sea-and river-type sockeye
that may serve as colonizers in the future. This line of research is
particularly important given expected habitat alterations from climate change.

9. Very few data were available to assess population
viability of sockeye salmon in the Russian Far East, and we document a
significant reduction in escapement in recent years at a site within the
KamchatkaRiver basin that warranted an endangered
listing for this subpopulation. The leading threat recognized for this subpopulation
is overfishing. The situation has been exacerbated by an increase in
illegal fishing practices. We encourage the leading agencies in this region to
provide more open access to data, and supporting meta-data, for assessment
purposes. We also encourage development of new monitoring efforts throughout
the region and increased enforcement to reduce poaching. Many populations of
river-type sockeye exist, particularly in western Kamchatka,
and focused research on these populations will provide important insight into
the status of the species there.